1. Field of the Invention
The present invention relates to a centrifugal clutch designed to prevent the occurrence of noise such as squeaking due to vibration of a clutch outer cover during a stall state. A stall state occurs when a friction material of a centrifugal weight maintains a state of sliding contact with an inner periphery of a drum wall of the clutch outer cover.
2. Description of the Background Art
A known centrifugal clutch is designed to prevent squeaking of the clutch outer cover. This noise occurs due to vibration of the clutch outer cover. Prevention of the noise is achieved by fastening a vibration isolation ring to a cylindrical drum wall included in the clutch outer cover so that the vibration isolation ring surrounds the drum wall. Such types of clutches are disclosed, for example, in Japanese Laid-open Patent No. Hei 9-236140, Japanese Laid-open Patent No. 2002-39227, and the like.
The centrifugal clutch disclosed in Japanese Laid-open Patent No. Hei 9-236140 includes a vibration isolation ring formed substantially into a bowl shape through press forming. The vibration isolation ring is mounted to an outer periphery of a drum wall by applying pressure thereto. Because of limitations on the wall thickness of the vibration isolation ring, there is a limit to the vibration isolation effect. In the centrifugal clutch disclosed in Japanese Laid-open Patent No. 2002-39227, on the other hand, a simple cylindrically shaped vibration isolation ring is mounted to an outer periphery of a drum wall, allowing the wall thickness of the vibration isolation ring to be increased.
In general, the clutch outer cover tends to become deformed through repeated cold and heat cycles, which it undergoes as a result of the engagement and disengagement of the centrifugal clutch. A vibration damping effect of the vibration isolation ring is impaired when an open-end side of the drum wall is deformed, since the greatest vibration damping effect is achieved at this location. In the centrifugal clutch disclosed in Japanese Laid-open Patent No. 2002-39227, the deformation, resulting from subjection of the drum wall to repeated cold and heat cycles, is not considered.
In view of the foregoing problems, it is an object of the present invention to provide a centrifugal clutch designed to effectively reduce or prevent deformation of an open-end of a drum wall in a clutch outer cover, by using a vibration isolation ring that is increased in wall thickness.